1. Field of the Invention
The present invention is generally related to an outboard motor and, more particularly, to an outboard motor that incorporates both an exhaust gas recirculation system and an idle exhaust relief system.
2. Description of the Related Art
Those skilled in the art of outboard motors are very familiar with idle exhaust relief systems which provide an alternative exhaust passage to conduct exhaust gas away from the engine when the engine is operating at relatively low speeds. Those skilled in the art of internal combustion engines are generally familiar with exhaust gas recirculation (EGR) systems. Exhaust gas recirculation systems are widely used in conjunction with automobile engines to recirculate a portion of an exhaust gas stream back to an intake system of the engine. This recirculation is helpful in controlling certain types of exhaust gas pollutants.
U.S. Pat. No. 5,070,838, which issued to McKay on Dec. 10, 1991, describes an integrated idle air and exhaust gas recirculation system. The system has a single valve assembly to control both idle air and exhaust gas being supplied to the engine. The valve assembly has a solenoid actuated two-way valve for switching from air to exhaust gas as a source, and a metering valve for controlling the quantity of gas, either idle air or exhaust gas, allowed to enter the engine intake.
U.S. Pat. No. 5,163,295, which issued to Bradshaw on Nov. 17, 1992, describes a system for controlling exhaust gas recirculation in a pressure boosted internal combustion engine. A valve seat is provided in the EGR passage and a hollow actuator rod is moved by a pressure responsive diaphragm to control flow. The diaphragm senses boost inlet pressure in a chamber supplied through a port in the rod which extends through the boost air inlet passage. In another embodiment a restrictor valve is provided in the exhaust pipe downstream of the EGR passage. The valve is closed at idle to divert exhaust to the EGR passage. As boost pressure increases, a separate pressure tap supplies a second pressure responsive diaphragm to open the restrictor valve.
U.S. patent application Ser. No. 11/503,740, which was filed by Mizuguchi on Feb. 22, 2007, describes an exhaust purifier for a diesel engine. A controller for an exhaust purifier performs idle-up to increase the idle speed of a diesel engine when an intake air amount, which is based on the atmospheric pressure and the engine speed, is less than a reference air amount of when a throttle valve is completely open and an EGR valve is completely closed during the regeneration of the filter. The controller performs idle-up by increasing the amount of fuel injected from the fuel injection valves of the diesel engine.
U.S. patent application Ser. No. 11/513,104, which was filed by Pierpont on Mar. 6, 2008, describes a low idle exhaust gas recirculation system. The system is provided for reducing NOx emitted from the power source at low idle speeds. The power source has at least one combustion chamber, an intake manifold, a first exhaust manifold, and a second exhaust manifold. The exhaust recirculation system has as valve located in at least one of the first and second exhaust manifolds. The valve is movable to increase the temperature of an exhaust gas by directing exhaust gas from the at least one of the first and second exhaust manifolds to the intake manifold. Furthermore, the exhaust recirculation system has a controller configured to determine at least one power source condition indicative of an exhaust temperature and move the valve in response to the determination.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.